1. Field of the Invention
The present invention relates to a magneto-optical recording apparatus in which an information signal is recorded in such a manner that an optical head irradiates a magneto-optical recording medium with a light beam at the same time of applying a magnetic field to the magneto-optical recording medium by a magnetic head, particularly relates to a support mechanism for the magnetic head in which the magnetic field modulated by the information signal is applied to the magneto-optical recording medium.
2. Related Background Art
In the past, the magneto-optical recording apparatus adopting a magnetic field modulation method has been practically used in which, at the same time of applying the magnetic field modulated by an information signal to the magneto-optical recording medium having a magneto-optical recording layer by the magnetic head, the optical head irradiates an area to which the magnetic field is applied with the light beam.
FIG. 6 is a side view showing a schematic configuration of the conventional magneto-optical recording apparatus. In FIG. 6, a reference numeral 21 indicates a magnetic head support mechanism, a reference numeral 22 indicates an optical head, reference numeral 23 indicates a connecting member which connects the magnetic head support mechanism 21 to the optical head 22, and a reference numeral 24 indicates a magneto-optical recording medium.
The optical head 22 is provided with an objective lens 25 for irradiating the magneto-optical recording medium 24 with the light beam. A reference numeral 26 indicates a cartridge which covers the magneto-optical recording medium 24, and an opening W for exposing the magneto-optical recording medium 24 is provided in a part of the cartridge 26.
The magnetic head support mechanism 21 is a support mechanism which supports a magnetic head 30 applying the magnetic field to the magneto-optical recording medium 24. The magnetic head support mechanism 21 includes support members 34a and 34b for holding the magnetic head 30 at front ends of the support members 34a and 34b, a reinforcing member 36, and a holding substrate 37. A reference numeral 27 indicates a driving member which drives the magnetic head support mechanism 21, a reference numeral 28 indicates a magnetic head driving circuit which supplies current to the magnetic head 30, and a reference numeral 29 indicates an electric lead which supplies the current.
FIGS. 7A and 7B show the details of the magnetic head support mechanism 21. FIG. 7A is its top view and FIG. 7B is its side view. The magnetic head 30 includes a core 31, a coil 32 which is provided around the core 31, a slider 33 on which the core 31 and the coil 32 are mounted. The core 31 is made of a magnetic material, and an end face of the core 31 is formed so as to be opposite to the magneto-optical recording medium 24. The slider 33 is made of such a material as resin and ceramic having lubricity.
The pair of support members 34a and 34b is attached to the gimbals Ga and Gb for holding the magnetic head 30 at their front ends and the holding substrate 37 to form suspensions Sa and Sb which hold the gimbals Ga and Gb together with the magnetic head 30. A reinforcing member 36 is attached at an intermediate position between the holding substrate 37 and the gimbals Ga and Gb. Each of the support members 34a and 34b is formed by a single thin plate made of, for example, phosphor bronze or beryllium copper having elasticity, the gimbals Ga and Gb have a width ranging from 0.2 to 0.5 mm, and the suspensions Sa and Sb have the width ranging from 2 to 5 mm. The reinforcing member 36 is made of a resin material, and the holding substrate 37 is made of stainless steel.
The gimbals Ga and Gb are electrically connected to both ends of the coil 32 in the magnetic head 30 respectively, and the suspensions Sa and Sb are electrically connected to the electric leads 29 at an exposed portion of a square hole H formed in the holding substrate 37 respectively. As described later, since the support members 34a and 34b form a current supply path which supplies the current to the coil 32 in the magnetic head 30, electric resistivity of the support members 34a and 34b is small, and the support members 34a and 34b are formed by an integrated member made of a copper alloy which is easily connected by soldering.
At this point, the connection of the suspensions Sa and Sb to the holding substrate 37 should be quite strong, and both are electrically insulated from each other. Therefore, in a region for attaching the suspensions Sa and Sb, an insulating member 38 made of a resin material is integrally formed with upper side projections Pa1, Pa2, Pb1, and Pb2 so as to sandwich the suspensions Sa and Sb in the insulating member to cover the upper and lower surfaces of the suspensions with the insulating member. Holes are made in the holding substrate 37. After the projections Pa1, Pa2, Pb1, and Pb2 of the insulating member 38 are fitted into the holes in the holding substrate 37, portions upwardly projected from the holding substrate 37 are melted and attached to the upper surface of the holding substrate 37.
As shown in FIG. 6, the suspensions Sa and Sb are downwardly bended toward the opening W in the cartridge 26 at the position where the suspensions Sa and Sb are attached to the holding substrate 37, energization force of the bending causes the magnetic head 30 to load (press) onto the magneto-optical recording medium 24 within the opening W. The magnetic head 30 is unloaded (retracted) from the magneto-optical recording medium 24 by slidingly driving the driving member 27 in a direction shown by an arrow A, and abutting on the reinforcing member 36 to lift the reinforcing member 36, elastically deforming the suspensions Sa and Sb, and rotating the magnetic head support mechanism 21 as shown by an arrow B.
In the opening W of the cartridge 26, the optical head 22 is arranged on the lower surface side of the magneto-optical recording medium 24, and the magnetic head 30 is loaded (pressed) to the upper surface side of the magneto-optical recording medium 24 while the magnetic head 30 is opposite to the optical head 22. At this point, the magnetic head support mechanism 21 is downwardly tilted toward the inside of the opening W from a position above the upper surface of the cartridge 26. The positions of the magnetic head 30 and the optical head 22 are aligned and connected so that the center of the end face of the core 31 which is of the magnetic field generating portion is located on an optical axis Z of the objective lens 25 in the optical head 22 (at the position of a spot of the light beam formed on the magneto-optical recording medium 24).
The current from the magnetic head driving circuit 28 is supplied to the coil 32 in the magnetic head 30 through the electric lead 29, the suspensions Sa and Sb, and the gimbals Ga and Gb. When the support members 34a and 34b themselves of the magnetic head 30 are used as the current supply path, it is not necessary to provide and fix the electric leads along the gimbals Ga and Gb or to directly connect the electric leads to the magnetic head 30. Accordingly, rigidity of the electric leads 29 does not adversely affect mechanical characteristics of the support members 34a and 34b, particularly the gimbals Ga and Gb, and it is also easy to realize manufacture thereof.
In recent years, it is necessary to increase modulation frequency of the magnetic field, as recording speed of the information signal is improved. Therefore, there is a trend to decrease inductance by decreasing an area of the end face (magnetic field generating portion) of the core 31 in the magnetic head 30 opposite to the magneto-optical recording medium 24. At this point, since the area to which the magnetic field is applied is also decreased, higher accuracy of position is required between the magnetic field applied area and the spot of the light beam which the optical head 22 forms.
However, by vibration or impact which is applied to the magneto-optical recording apparatus from the outside, the magnetic head 30 is displaced in a direction parallel to the magneto-optical recording medium 24 in a state that the magnetic head 30 is loaded.
Further, since the support members 34a and 34b holding the magnetic head 30 have the shape which is downwardly tilted toward the inside of the opening W from a position above the upper surface of the cartridge 26, the magnetic head 30 is displaced not only in the vertical direction but also in the horizontal direction relative to the magneto-optical recording medium 24 by fluctuation in height of the surface of the magneto-optical recording medium 24 or surface run-out associated with rotation.
The above-described action will be described referring to FIG. 8. In FIG. 8, the position of each member displaced upwardly from the position shown by solid lines is shown by alternate long and short dashed lines. When the surface of the magneto-optical recording medium 24 is displaced in the vertical direction, the overall support members 34a and 34b generate rotational displacement about the position for attaching the suspensions Sa and Sb, which results in the arc displacement of the magnetic head 30 as shown by an arrow C.
The horizontal displacement associated with the rotational displacement is proportional to the magnitude of the tilt of the support members 34a and 34b relative to the magneto-optical recording medium 24. However, there is limitation in a manner that the tilt angle of the support members 34a and 34b is decreased, by arranging the support members 34a and 34b so as to be downwardly tilted toward the opening W from a position above the upper surface of the cartridge 26. Since the gimbals Ga and Gb and the suspensions Sa and Sb are made of a single member, it is difficult that the characteristic of the gimbals Ga and Gb sufficiently elastically holding the magnetic head 30 is compatible with the characteristic of the suspensions Sa and Sb suppressing the rotational displacement because both characteristics are different from each other.
The end face of the core 31 is also displaced relative to the optical axis Z of the objective lens 25 in the optical head 22 by the displacement caused by the vibration or the impact of the magnetic head 30 or the horizontal displacement of the support members 34a and 34b associated with their rotational displacement. Therefore, even if these displacements are generated, the magnetic field applied area must have a sufficiently wide area including the estimated amount of displacement so that the spot of the light beam is formed within the magnetic field applied area.
Usually, a size of the magnetic field applied area is approximately equal to the size of the end face of the core 31 in the magnetic head 30. That is to say, since the lower limit of the size of the end face of the core 31 is determined by the amount of horizontal displacement of the magnetic head 30, the inductance of the magnetic head 30 can not be sufficiently decreased. This results in a stumbling block for improvement of the recording speed of the information signal.
Since the support members 34a and 34b also have a function of the current supply path to the magnetic head 30, each electric resistivity of the support members 34a and 34b is small and the support members 34a and 34b are formed by the integrated member made of the copper alloy which is easily connected by soldering. However, the electric insulation is required by attaching the support members 34a and 34b via the insulating member 38 to the holding substrate 37 made of the metal material. The provision of the insulating member 38 becomes a problem for miniaturization, because the height in the magnetic head support mechanism is increased. Since the height in position for attaching the suspensions Sa and Sb is also increased, the tilt of the support members 34a and 34b is also increased. As a result, there is a problem that the horizontal displacement of the magnetic head 30 associated with the rotational displacement is increased more and more.